Catalytic cracking of hydrocarbons



oct; 27, 1942.

w. L. BENEDlc-r CATALYTIG CRACKING 0F HYDROCARBONS Filed pee. a, 1939 um@N SQENN v nickel, cobalt, etc.

Patented ct. 27, 1942l UNITED ASTATES PATENT OFFICEl CATALYTIC CRACKlNGOF HYDROCARBONS 4 Wayne L. Benedict, Chicago, Ill., assignor toUniversal Oil Products Company, Chicago, Ill., a corporation of Delaware'Application neeembers, 1939, serial No. 308,157

(c1. iss-49) 7 Claims.

This invention relates to a process for converting hydrocarbon oil intosubstantial yields of desirable products including gasoline of highantiknock value. Although the charging stock is usually of petroleumorigin, similar stocks from other sources may also be-converted.Normally, distillates which can be distilled at ordinary pressureswithout substantial decomposition are used, and these include naphtha,kerosene, gas oil and the like.

The use of thermal non-catalytic processes for converting high boilinghydrocarbons into increased yields of gasoline and gas has beenpracticed and the reactions involved are fairly well understood. Whenemploying catalysts to assist in such converions, however, knowledge ismuch less complete and as a consequence, a discussion of such reactionsis best kept to a factual basis.

Various catalytic agents have been proposed for catalytic crackingreactions, among which are the reduced metal catalysts, including iron,These catalysts are subject to poisoning by sulfur compounds containedin the oils undergoing conversion, and moreover, tend to promote gas andcarbon-forming reactions. Another type of catalytic agent which hasfound application is the naturally-occurring clay type which has beenactivated by treatment with acids or other chemicals.

Still another type of catalyst, which is the preferred catalyst of thepresent invention, vis the so-called silica-alumina, silica-zirconia,and silica-alumina-zirconia type catalyst. These are syntheticcomposites prepared by the separate or simultaneous precipitation of thecomponent materials, followed by washing, drying and calcining steps toproduce afinishedv catalytic agentof a high degree of activity.

The conditions under which the catalysts are employed for catalyticcracking range from approximately 500-1200 F. and pressures ofsubstantially atmospheric to 1000 pounds per square inch. Thetemperature is of considerable importance in determining not only theamount but also the type of reaction which takes place, sincegasolinesof entirely different character may be obtained by varying the operatingconditions even though the amount of conversion per pass on vapercentage basis 'may remain substantially the same. For example, whenoperating in the range of' 50G-900 F. and50-1000 pounds per.

square inchV pressure, a substantially oleiin-free gasoline suitable inall respects for use in aviation motor fue1 is obtainable. Attemperatures above 900 F. and at pressures of the order of atmosphericto -150 pounds per square inch, gasolines containing substantial amountsof olen hydrocarbons are obtained.

The lower temperature cracking operation is subject to certaindisadvantages from an operating standpoint, and these are largelyconnected with the diierence in temperature level necessary forprocessing and for vcarrying out the reactivation step. Since thecatalytic agents become carbonized at intervals, it is necessary toreactivate them periodically by treatment with an oxygen-containing gasat a temperture in excess of 900 F. The temperature of reactivation isusually of the order of 1200-1400" F. but it is necessary that the massof the catalyst be increased to a temperature of approximately 900 F. orhigher before burning begins. Moreover, under the lower temperatureconditions a certain amount of hydrocarbon oil is adsorbed in thecatalytic mass, and, being insufficiently removed, is destroyed in thesubsequent reactivation st'ep with resultant relatively high volumetriclosses. The present invention is a method of overcoming the difficultiesof low temperalture cracking, reducing the losses, and increasing theefiiciency of the operating cycle.

In one specific embodiment the present invention comprises a process forconverting hydrocarbon oil into substantial yields vof gasoline suitablefor use in aviation fuel which comprises contacting said hydrocarbon oilwith a cracking catalyst in a. plurality of cracking zones seriallyarranged wherein the following repeated sequence of steps is carried outat each of said cracking zones comprising a primary step of crackingsaid hydrocarbon oil at a temperature of 50G-900 F, and a pressure ofapproximately 50-1000 pounds per square inch to produce a substantiallyolefin-free gasoline, a secondary step of heating the insufficientlyconverted portion of reaction products from said primary step' toavtemperature within the range of approximately 9501200 F. andvcontacting it with partially spent cracking catalyst previously used insaid primary step to increase the temperature of said cracking catalystto approximately 900 F., and a tertiary step of reactivating thecracking catalyst used in said primary and secondary steps by treatingit with an oxygen-containing gas at a temperature within the range of900-1500 F., fractionating the reaction products from said primary stepinto gas, gasoline and insufliciently converted oil, heating andsupplying the insuiliciently converted oil to said secondary step, andsupplying the reaction products from said secondary step to said primarystep.

In addition to the three steps described, a fourth step in which thecatalyst is'oooled from the reactivationtemperature to the operatingtemperature may be included. This step is not tus. No attempt has beenmade to proportionate the equipment or to draw it to an exact scale.

Referring to the drawing, hydrocarbon oil is charged through linel,valve 2,pump t, valve l to coil 5 which is disposed in heater t. Afterbeing heated to a temperature within the range o 500- 900 F., it ispassed'through line l, valve It, line 9 and valve l0 to catalyticreactor ll which may be any suitable type of reactor such as manifoldedtubes or a chamber or tower containing catalyst particles therein. Thereaction products pass through line l2, valve le to line id and thenceto fractionator l5. Gasoline and gas are removed through line lt andvalve il. A residual oil may be withdrawn through line l@ and valve i9,although it is withinthe scope of the invention that all of theinsumciently converted oil should be returned through line 2u, heatexchanger 2l, valve 22, pump 23, valve tl to coil which is disposed inheater 2t. if desired, additional oil may be introduced into line 20through line 2l and valve 2d, although this is not usually done. The oilis heated to a tern perature within the range of 900l200^l2 andpreferably of the order of l000 F., and passed through line is and valve@t to line 3l and valve 32 to reactor This reactor has previously beenused for converting hydrocarbons in the lower temperature range. Thepressure is reduced to. substantially atmospheric or slightlysuperatmospheric, and the cil which is at the higher temperatureincreases the temperature ci the catalyst to a point substantially inexcess or" 900 F. The reaction products pass through line til and valve.t5 to line and thence to :dash chamber 3l. Residual oil may bewithdrawn through line 38 and valve The vapcrous revalve lel and line49. The next regular sten conaction products pass through line d0, heaterrchanger di and valve lll to line i, and are thus returned to theprimary reaction step being carried out in reactor il. Atthe same time.reactivation gases containing oxygen are passed through line 4t, line@it and valve d@ to reactor Il@ which is substantially identical withreactors lll and 33, and which has previously passedthrough both theprimary and the secondary steps of the cycle. The reactivation gasespass throughllne 41 and valve 48 to line te, and are either vented tothe atmosphere or recirculated in part by means 'not shown. After asuitable interval or time determined by the activity of the catalyticagent in the primary reaction step, the valve settings are changed andthe next phase'of the cycle begins. The heated hydrocarbon oil from line1 is introduced into reactor d@ through line and valve 5I and areremoved to ractionator I5 through line 52, valve t3 and line it. Theinsumciently converted oil from line 2s is introduced into reactor i lthrough line M and valve 55, passing thence through line 58 and valve 5lto line 36, ilash chamber, 3l and by previously describedroutes to linel. Reactivation gases from line 43 pass through-line 58 and valve E9 toreactor 33 and are removed through line 80,.

sists in processing in reactor 33, increasig reactor d@ to the hightemperature range, and reactivating reactor ll. This is accomplished byintroducing hydrocarbon oil through line 52 and valve et to reactor 33,removing the reaction products through line 66, valve t5 and line I4 tothe fractionator. The heated recycle oil is introduced from line 29through line e@ and valve Gl to reactor d@ andthe cracked productsremoved through line te and valve 69 to line t6 and thus recirculated.Reactivation gases are passed through line d3, line 'lil and valve li toreactor il, being removed through line l2, valve 'i3 and line 39. Thecycle is completed and the next cycle is begun by returning the valvesto the original settings so that reactor it is processing at lowtemperature, reactor 33 is being increased to the high temperaturerange, and reactor l0 is being reactivated.

The drawing has been simplified by omission or various auxiliaryequipment such as stabilizers, heat exchangers, condensers, etc.

In addition to the advantages mentioned in the foregoing specifications,the process has the advantage that during the secondary step while thetemperature of the catalyst is being increased from that in theprocessing region to thereactivation range, a considerable portion ofthe recycle oil h converted to .gasoline and gas incidental to theoperation. lThe gasoline produced is relativehr olenic, but lupon beingpassed through the primary stage this is converted to substantiallyolen-free motor fuel.

The following example illustrates the usefulness and practicability ofthe process but should not be construed as limiting it to 'the exactconditions employed therein.

.d Mol-Uontinent gas oil may be converted according to the methoddescribed in the foregoing specliicaticn, the insumciently converted oilbeing recycled by way ofthe high temperature step. The 'main processingstep may suitably be carried out at a temperature of 800 F. The catalystin the secondary step is heated to a temperature of 'approximately 900F. by heating the recycle oil to 950 F. and passing it over thecatalyst. Reactivation is begun at 900 F., and reached a maximumtemperature of about 1300 F. A fourth reaction zone may be provided toallow cooling of the catalyst from the temperature oi reactivation toapproximately 800 F. before resuming processing. Atotal yield of 65% ofsubstantially saturated cracked gasoline may be obtained in this manner,the remainder being gas, and oil suitable for furnace distillate. Thereis an average o d'%5%'of unaccounted for loss. When operating in theusual manner without the step of passlng heated and cracked recycle overthe catalyst bed in the v.primary cracking step, the loss amounted toapproximately 12% of the oil charged.

' I claim as my invention:

l. A process for converting hydrocarbon oil into substantial yields ofvaluable products lncluding gasoline which comprises maintainingcracking catalyst in a plurality of catalytic reac tion zonessimultaneously operated in a plurality of concomitant steps comprising aprimary step of contacting said hydrocarbon oil with a. crackingcatalyst under conditions of temperature and pressure adequate to effectsubstantial conversion thereof to relatively oleiln-Iree gasoline, asecondary step of heating insuvtllciently converted oil from the primarystep to a temperature within mina-zirconia.

the range of approximately 950-1200 F. and contacting it with crackingcatalyst previously used in said primary step to increase thetemperature thereof to a point above approximately 900 F. and to formolefinic gasoline, a tertiary step of reactivating said crackingcatalyst previously used in said primary and secondary steps by treatingit with an oxygen-containing gas at a temperature of approximately.90o-1500 F. before cooling thereof to below approximately 900 F. and aquaternary step of returning the temperature of said reactivatedcatalyst to the operating temperature of said primary step,fractionating the reaction products 'from said pri-- mary step into gas,gasoline and insuillciently converted oil, recycling at least a` portionof said insufficiently converted oil to said secondary step, andsupplying olenic gasoline from said secondary step to said primary step.

2. A process for converting hydrocarbon oil into substantial yields ofvaluable products including gasoline, suitable for use in aviation motorfuel which comprises maintaining cracking catalyst in a plurality ofcatalytic reaction zones simultaneously operated in a plurality of conlcomitant steps comprising a primary step of contacting said hydrocarbonoil with a cracking catalyst at a temperature M500-900 F. and a pressureof approximately 50-1000 pounds per square inch to produce asubstantially olefin-free gasoline, a secondary step of heatinginsuiiiciently converted oil producedl in said primary step to atemperature within the range of approximately QSO-200 F. and contactingit with the cracking catalyst previously used in saidl primary step toheat said catalyst to a temperature in excess of 900 F. and to formoleflnic gasoline, a tertiary step of reactivating the cracking catalystwhich has previously passed through said primary and secondary steps bytreating it withv an oxygencontaining gas at a temperature oiapproximately 9001500 F. before cooling thereof to below approximately900 F. and a quaternary step of returning the temperature of saidreactivatedcracking catalyst to a temperature within the range of saidprimary step, viractionating the reaction products irom said primarystep into gas, gasoline and insuilciently converted oil, heating andsupplying at least a portion of the insumciently convertedoil to saidsecondary step, and passing oleflnic gasoline from said secondary stepto said primary step.

3. The process of claim 1 wherein the cracking catalyst is selected fromthe group consisting of silica-alumina, silica-zirconia, andsilica-,alu-

4. A process for converting hydrocarbon oil into substantial yields ofvaluable products including a relatively olefin-free motor fuel whichcomprises converting said oil in a plurality of catalytic reaction zonessimultaneously operated in a repeated sequence of steps comprisingcontacting said hydrocarbon oil with a cracking catalyst at atemperature and pressure adequate to effect substantial conversionthereof into relatively oleiln-iree gasoline in a primary reaction zone,fractionating the reaction products into gas, gasoline andinsuillciently converted oil, heating at least a portion of saidinsutllciently4 converted oil to a temperature of approximately 950-1200F. and contactingit in a secondary reaction zone with cracking catalystpreviously used in the production of relatively oleiln-free gasolinefrom said hydrocarbon oil, supplying oleflnic gasoline formed in saidsecondary zone 75 to said primary reaction zone, reactivating thecracking catalyst in a tertiary reaction zone by contacting it with anoxygen-containing gas at a temperature of 900-1500 F., periodically di-5 ,verting the flow of said hydrocarbon oil to said iiow of saidinsuiciently converted oil to said primary reaction zone at atemperature of 900'- F., supplying olefinic gasoline tion zone whilereactivating the catalyst in said secondary reaction zone by treating itwith an oxygen-containing gasperiodically diverting the flow of saidhydrocarbon oil to said secondary gas and iinally completing the cycleby directing the flow of said hydrocarbon oil to said primary reactionzone, directing the flow of said insufficiently converted oil to saidsecondary reaction zone and the iiow of said reactivation gases to saidtertiary reaction zone. 5. A process for converting hydrocarbon oil intosubstantial yields of valuable products including high antiknock motorfuel which comprises maintaining cracking catalyst in a plurality ofcatalytic reaction zones simultaneously operated in a plurality ofconcomitant steps, comprising a primary step of contacting saidhydrocarbon oil with a cracking catalyst at a temperature and pressureadequate to eiect substantial conversion thereof to relativelyoleiinfree gasoline, a secondary step of heating insufi ficientlyconverted oil produced in said primary step to a temperature within therange of approximately 950-1200 F. and Acontacting it with .40 thecracking catalyst previously used in said primary step to heat saidcatalyst to a temperature in excess of 900 F., a tertiary step ofreactivating said catalyst which has been previously used in saidprimary and secondary steps by treating it 4r with an oxygen-containinggas at a temperature of approximately 900-1500" F. before coolingthereof to below approximately 900 F., iractionating the reactionproducts from said primary step into gas, gasoline and insufdcientlyconverted oil, heating and supplying a portion of said insumcientlyconverted oil to said secondary step, passing the reaction products fromsaid secondary step to a flashing zone, separating and passing thevaporous portion of said reaction 5, products to said primary step andremoving the residual portion of said reaction Products from saidilashing zone.

6. A process for converting hydrocarbon oil into substantial yields ofvaluable products in- 6 cluding high antiknock gasoline which comprisesmaintaining cracking catalyst in a plurality of catalytic reaction zonessimultaneously operated in a pluralityvof concomitant steps comprising aprimary step of contacting said hydrocarbon oil, with a crackingcatalyst at a temperature and pressure adequate to effect substantialconversion thereof into relatively olen-free gasoline, a secondary stepof heating insuiciently converted oil produced insaid primary step to atemperature within the range of approximately 950-1200 now formed insaid primary zone to said tertiary reac secondary `steps by treatingitwith an oxygencontaining gas at a temperature of approximately 900-1200F. before cooling thereof to below ap-y proximate range of 50o-900 F'.to produce gaso line of rela-tivelylow oleiin content, then con tactingsaid body of catalyst with hydrocarbon oil heated to a temperature ofabout S50-i200 F. to produce gasoline of higher clen content Y than theiirst-named gasoline and to raise the temperature of the catalyst bodyto that at which. combustion of carbonaceous matter, deposited on thecatalyst during the aforesaid conversion steps, will be initiated in thepresence of oxygen,

Aand then vcontacting said body of catalyst with oxygen-containing gasto burn carbonaceous matter from the catalyst and thereby reactivate thelatter.

